Police reports say the child was running from the south side of 104 Kale Street to the north side, when he was struck by a semi-truck driving westbound on the road.
The boy was reportedly with his grandmother, and running to his mother on the other side of the street when he was hit, said Washington State Patrol spokesman Trooper Mark Francis.
Medics transported the child to Seattle Children's Hospital in critical condition. His current condition will be made available later Sunday.
No charges will be filed.